MegaMod is many times larger than the vanilla game itself, and takes ages to load. 10 minutes isn't super surprising as a loading time for it. It loads slower under DirectX9 but is more stable. DX11 is a tad faster, but causes crashes for some people.
From what someone else recently posted, it's mostly the RAM size that helps with the loading times for such a big mod. I indeed noticed a small change on my laptop when I went from 4 to 8GB of RAM. Loading times that were 15+ minutes are now merely 10+... Ouch.
Basically, if it hasn't given you an error message, it's still doing its stuff. The only way to speed the loading up is to clean up memory used before launching, so closing everything else before. Then go and make yourself a cup of tea and grab food to be ready for a long playing spree while Banished does its slow loading thing.
You could try to play with "just" <abbr title="Colonial Charter">CC</abbr> first to see what kind of loading times you have for that already big mod. If <abbr title="Colonial Charter">CC</abbr> loads slowly but works, <abbr title="MegaMod">MM</abbr> should work too, but with a much longer loading time. It would give you a rough idea of what to expect when it comes to loading speed.
Side note: After enabling <abbr title="Colonial Charter">CC</abbr> or MegaMod (or any other mod, or even just changing your mods' load order) in-game, you'll need to entirely exit Banished and relaunch before starting a new town. If you don't do that extra step, you're likely to crash whenever you quit your town. It's better to suffer an extra time through the loading screen than to have crashes later on.
